Anybody who grows perennials in their garden is familiar with the idea of cutting off the dead tops of their plants in late fall or early spring. By nature, most flowering perennials will die back to ground level in the fall, leaving behind their dried-up tops; cutting these back at the appropriate time is a familiar and easily understood task.There are many other pruning techniques that gardeners can make use of at other times of the season, in an effort to coax the best possible performance and garden worthiness from their perennials. These are less familiar tasks to most gardeners, but worth exploring at this point in the season when a quick and timely trim can produce some amazing results. I've broken the techniques into a few basic groups. Deadheading This idea is a simple one and fairly familiar: by trimming off the faded flowers, many perennials can be coaxed into producing more buds and flowers, rather than wasting their energy forming seeds. For certain plants (peonies, for instance), although no amount of deadheading will trick them into repeat bloom, plants look so much better after deadheading that it becomes part of the regular list of summer chores. New gardeners often ask us how far down to cut below the flowers, but unfortunately it's not always an easy thing to explain, each type of plant responding in a slightly different way. Experimentation is the best way to learn this; after playing around with it for awhile, most gardeners sort of develop an instinct about where exactly the cut should be made. A few general tips:
- Don't cut off any developing flower buds. This sounds obvious, but sometimes the buds are not always large and easy to find -- they may be hiding among leaves or very tiny. Follow the stem down below the faded blooms to see if any new flower buds are present. Cut off the faded flowers along with the stem to just above these new buds. With plants like Coreopsis 'Moonbeam', the buds are usually held just below the faded blooms, and a pair of hedge shears comes in handy for this task: just lightly shear the very outside of the mound, taking off the finished blooms and leaving the buds to come on later. If no buds are present, then a slightly lower shearing will encourage new ones to form in due time. Deadheading the individual blooms of a small-flowered plant like 'Moonbeam' with hand pruners would be tedious, to say the least.
- Perennials with heads of flowers, or with daisy-shaped flowers usually look better if at least some of the stem below the bloom is cut off, along with the faded flowers. This helps to avoid that unpopular "decapitated" look. Cut these back to a thicker main stem, where new buds are probably already forming. Perennials that respond well to this include Purple Coneflower (Echinacea), Shasta Daisies (Leucanthemum), Rudbeckia, Yarrow (Achillea), Blanket Flower (Gaillardia) and Beebalm (Monarda).
- Deadhead individual flowers, when new buds are forming on the same stem: this is necessary for Daylilies (Hemerocallis), Peach-leaved Bellflower (Campanula persicifolia), Balloon Flower (Platycodon) and a few others.
- Deadhead any plant that self-seeds around, if you wish to prevent this from happening. Good candidates include: Columbine (Aquilegia), Sweet William (Dianthus barbatus), Common Yarrow (Achillea millefolium), Perennial Bachelor's Buttons (Centaurea), Jacob's Ladder (Polemonium).